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Commands used in Dockefile - Part4

  Docker is an opensource tool used for virtualization and deliver software in the form of packages called Containers. It is one of the most important tools used in networking domain.  Dockerfile  is a template for building the image which contains commands needed to package the software. In this post, I am going to explain the commands ADD & COPY used in  Dockerfile .   ADD Command:   ADD command is used to copy files, directories or files from remote URLS to destination path in the image. The source paths can contain wildcards.   If the destination has relative path, it is relative to the Working directory of the image. Note that source path is always relative to the Docker build context.   ADD command will not support authentication. So, if there are any protected files to be added in  Dockerfile  building, use other tools like curl or  wget   Dockerfile  copying Single & Multiple files, directory using ADD inst...
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Notes on IPv4, IPv6 and MAC representations

 In companies related to networking domain, “Explain IPv4, IPv6 and MAC” is one of the common questions asked in technical interview. This post provides overview of these concepts.

IP:

IP is the protocol used in Networking layer. It is responsible for the delivering packets from source to destination based on the identifier known as IP address of the device. There are two popular ways of representing the devices in the network. They are:

  1. IPv4 (Internet Protocol version 4)
  2. IPv6 (Internet Protocol version6)


IPv4: 

This version of IP uses 32-bit addresses to identify the device on the network. Therefore, the total number of addresses possible with IPv4 is 232. These 32-bit addresses are divided into 4 octets (batch of 8 bits) with each octet represented in decimal numbers and octets are separated by dot.


In IPv4 the loopback address of a device is 127.0.0.1. IPv4 supports unicasting, broadcasting and multicasting. To map IPv4 address to MAC, IPv4 uses Address Resolution Protocol (ARP). Internet Protocol Security (IPsec) is optional in IPv4.


In the modern world, lot of technological evolutions like IoT, ML are happening. As a result, IPv4 will not be sufficient to identify the devices in the network. So, another version of IP known as IPv6 is developed and transitions are going on to move from IPv4 to IPv6.


IPv6: 

This version of IP is developed to deal with address exhaustion problem of IPv4. It uses 128-bit addresses to identify the device. IPv6 addresses are represented using hexadecimal numbers. So, this representation contains 8 blocks where each block contains 4 hexadecimal digits and blocks are separated by colon (:).


In IPv6 the loopback address of a device is ::1. IPv6 supports unicasting, multicasting and anycasting. To map IPv4 address to MAC, IPv6 uses Neighbor Discovery Protocol (NDP). Internet Protocol Security (IPsec) is optional in IPv6.


Dual Stack:

Communication between IPv4 and IPv6 is not possible. But both IPv4 and IPv6 can exist on the same network which is called as Dual Stack.


MAC:

MAC (Medium Access Control) addresses are used to uniquely identify a Network Interface Controller on as system (NIC). The size of the MAC address is 48 bits and represented in blocks of hexadecimal digits where each block size is and are separated by colon (:). First 6 hexadecimal digits represents the manufacturer called as Organizational Unique Identifier. The Last 6 hexadecimal digits represents the NIC and are assigned by the manufacturer.


To find MAC address on the Windows system use ipconfig/all. To find the same in Linux system use ifconfig –a.


Please feel free to comment the things you think to be added to the post. 

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